The inventive concept relates to magnetic recording media. More particularly, the inventive concept relates to a perpendicular magnetic recording medium in which the direction of magnetization of bits of recorded data is perpendicular to the surface of a magnetic layer.
The amount of information or data that must be processed by today's electronic devices is forever rapidly increasing. Accordingly, the data must be recorded (stored) with a high-density and the data must be capable of being recorded/reproduced at a rapid rate. In this regard, magnetic recording devices have characteristics such as large storage capacity and fast access time. Accordingly, magnetic recording devices are being widely used as information memory devices by various digital devices, as well as by computers. These magnetic recording devices employ a magnetic recording medium to record (store) data. Magnetic recording media have a number of tracks along which data is recorded, and bits of data are recorded along each of the tracks.
A magnetic recording medium of a magnetic recording device may be of a longitudinal magnetic recording type or a perpendicular magnetic recording type according to the way in which the medium records (stores) data. In a longitudinal type of magnetic recording medium, the direction of magnetization of bits of recorded data is parallel to a surface of a magnetic layer. In a perpendicular type of magnetic recording medium, the direction of magnetization of bits of recorded data is perpendicular to the surface of the magnetic layer. Data can be recorded with a higher recording density on a perpendicular type of magnetic recording medium than on a longitudinal type of magnetic recording medium.
A conventional perpendicular type of magnetic recording medium includes a soft magnetic underlayer, a recording layer, and a passivation layer. In order to maximize the recording density of a perpendicular type of magnetic recording medium, it is necessary to minimize the width of the tracks and to minimize the number of bits which can be recorded along a unit length of each track. To these ends, the recording layer must have a small grain size. Meanwhile, the smaller the grain size of the recording layer, the higher the perpendicular magnetic anisotropy energy (Ku) of the material forming the recording layer must be if the recording layer is to remain thermally stable. However, it is generally known that a coercive force of the recording layer becomes greater the higher the perpendicular magnetic anisotropy energy (Ku) becomes. Also, it is generally known that as the grain size of the recording layer becomes smaller the saturated magnetization (Ms) of the material forming the recording layer has to be increased to assure a necessary data reproduction output. Also, it is generally known that it is very difficult to produce a recording layer having uniform magnetic characteristics because the magnetic characteristics of the recording layer vary according to the size of the grains of the recording layer and it is very difficult to produce a recording layer having grains of the same size.